The present invention relates to transfer hoist systems for use by a disabled person, providing him with independent mobility. The invention also provides an assistive device for transporting disabled persons for use in hospitals, clinics, nursing homes, etc.
Transfer hoists for disabled persons are typically used by paraplegic, quadriplegic, handicapped, weak, or elderly persons to transport themselves from one place to another, such as from a wheelchair to a bed, without assistance from others. Unfortunately, most prior art transfer hoist systems tend to be modeled after industrial hoist systems and, consequently, are not satisfactory for use in domestic settings. For example, a typical safety mechanism found in industrial hoists causes the hoist to hold or freeze upon sensing a malfunction, leaving the load literally hanging in air.
Prior art hoists are commonly mounted on and suspended from overhead rails which are secured to ceiling joists. For example, Twitchell et al., U.S. Pat. No. 4,243,147, Jan. 6, 1981, discloses a three-dimensional lift system wherein rails are permanently secured to the ceiling. There are several disadvantages associated with ceiling-mounted systems. Since the joists must support the weight of the hoist support, the hoist, and the person being lifted, the joists themselves must be extremely strong. Reinforcement of existing ceiling joists is sometimes required. Ceiling-supported systems are also permanent. If a disabled person moves to a new residence, travels to visit friends or relatives, or even desires to stay at a hotel, he cannot simply pack up the hoist system and take it with him. Even within his own residence, if the user wishes to change bedrooms, for example, he cannot easily move the ceiling-supported transport system to his new room.
Another common problem associated with prior art hoists is that the hoists are frequently supported by a single I-beam. The trolley wheels cf the hoist usually engage and track on the upper surfaces of the lower flange portion of the I-beam, (see, e.g., McCord, U.S. Pat. No. 4,372,452, Feb. 8, 1983). Unfortunately, I-beam supported hoists are somewhat unstable in that they permit swinging of the disabled person. This "pendulum" effect of I-beam or single rail supported systems can be disconcerting and even dangerous to handicapped individuals.
Floor mounted hoist systems also have disadvantages. To ensure stability., floor mounted systems necessarily require that a large surface area be reserved for placement of the legs of the support structure. For example, Simmons et al., U.S. Pat. No. 4,296,509, Oct. 27, 1981, discloses a dual-tripod supported invalid lift. The tripod renders a rather large triangular area of floor space unusable for any other purpose, and the structure itself is inhibitive of someone attempting to assist the invalid, i.e., it simply "gets in the way". Floor mounted structures also pose serious headroom problems as well. Since the hoist support rails are necessarily lower than the ceiling, the disabled person often has little room between his head and the support rails. In some designs where the harness swivels or swings, as in single rail supported systems, the invalid is in danger of bumping his head.
One device which has apparently solved the instability problem of swinging or swiveling harnesses is an invention disclosed by Hachey et al., U.S. Pat. No. 4,627,119, Dec. 9, 1986. Unfortunately, this floor mounted support structure appears to require a specific harness and is not easily adaptable to other harnesses. Moreover, since the harness is not rotatable, the orientation of the person is fixed as he is transported between the wheelchair and the bed. This is disadvantageous since it is sometimes desirable to change the orientation of a person after leaving the wheelchair but before entering the bed. Another drawback of this device is that the support structure is wider than the person, again utilizing a relatively large floor space as is common in floor-mounted systems.
Perhaps the most important failure of prior art systems is their safety mechanisms. Disabled persons are especially vulnerable to a variety of potentially harmful conditions and events. Systems to aid handicapped persons must necessarily provide safety means to compensate for the user's disabilities. Unfortunately, many prior art devices do not adequately protect the handicapped individual. This shortcoming is probably attributable to the fact that many designs for hoist systems for the disabled are borrowed from industrial applications.
In particular, there are two potential malfunctions or problems which are typically associated with hoist systems for disabled persons. The first potential problem is that of a system power failure occurring during the hoist operation. The safety mechanism of the Twitchell et al. invention, discussed above, is typical of prior art solutions, in that the motor and transmission of the hoist become locked upon loss of power. Thus, in the event of a power failure, the disabled person is literally "left hanging" in a somewhat vulnerable position. Other prior art devices provide for a manual override of the hoist in the event of power loss. Unfortunately, manual override schemes typically utilize a hand crank for manually lowering the disabled person. This crank is usually not within easy reach of the suspended person, and, in any event, usually requires a second person to operate.
A second potential problem occurs when a disabled person encounters difficulty during the hoisting process. Many difficulties are readily imaginable. For example, the person may drop the control unit for the hoist and be unable to retrieve it; the user may faint or become otherwise incapacitated; the system itself may develop a malfunction short of complete power failure. Prior art devices have not provided a satisfactory solution to this problem.
Thus, it is seen that there has existed a long-felt need for a better hoist system for disabled persons.